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1.
We have studied the organic superconductor (TMTSF)2PF6 using 1H nuclear magnetic resonance. The spin-lattice (T1) and the spin-spin relaxation time (T2) measurements manifested a divergence associated with a structural phase transition at 160 K. 相似文献
2.
The effect of a transverse magnetic field on the chain axis resistivity of the new organic conductor (TMTSF)2PF6 is found to be substantial near the transition point. δρ/ρ0 is + 20% at B=6Vsm-2 just above the transition. An interpretation based on curvature in the Fermi surface is proposed. 相似文献
3.
The ESR g-factor, linewidth and spin susceptibility of (TMTSF)2PF6 are each found to have a distinct temperature dependence. The anisotropy of g and of the linewidth for static magnetic fields in the plane perpendicular to the highly conducting axis suggest that spin-phonon scattering is the dominant relaxation mechanism. The metal-insulator transition at 19 K is reflected particularly clearly in the magnetic properties. 相似文献
4.
We present ESR experiment on irradiated TMTSF-DMTCNQ and (TMTSF)2PF6. They suggest that a weak disorder extends the metallic phases to low temperatures. Surprisingly, disorder has no effect on the ESR linewidth of (TMTSF)2PF6 between 20 and 30 K, where the d.c. conductivity changes a lot with disorder. 相似文献
5.
Wafa Kaddour Pascale Auban-Senzier Claude Pasquier Lydie Valade 《Physica B: Condensed Matter》2012,407(11):1715-1717
The 1D organic salt TTF[Ni(dmit)2]2 becomes superconductor with Tc=1.6 K under an applied hydrostatic pressure of 7 kbar. Structural determinations in this system lead us to suspect that superconductivity (SC) coexists with a charge density wave (CDW) instability at low pressure. In order to better understand how SC emerge from a CDW and to revisit the pressure–temperature phase diagram of the TTF[Ni(dmit)2]2 we performed transport and thermoelectric power measurements under pressure. 相似文献
6.
The temperature dependence of the resistivity of (TMTSF)2PF6 over the temperature range 25–300 K is in excellent agreement with “libron” theory, if a Bloch (1-phonon) contribution corresponding to λ = 0.16 (a value determined from the Peierls transition temperature) is invoked. This contributes about 10% to the resistivity at 300 K, and about 20% at 40 K. 相似文献
7.
Electron spin resonance and electron–proton double resonance (Overhauser shift method) are used for the comparison of proton radiation damaged and as-grown (fluoranthene)2PF6 single crystals. Chemical modification and various consequences of the nonuniform distribution of radiation induced defects in this quasi-one-dimensional organic conductor with defect dependent Peierls transition are worked out. 相似文献
8.
Magnetic susceptibility was measured on a bundle of single crystals of difluoranthene phosphor hexafluoride [(FA)2·+PF6?] with external field parallel or perpendicular to the molecular stacking direction. Except for lowest temperatures, where the paramagnetic contribution of sample defects is of importance, magnetic susceptibility is dominated by the strongly anisotropic molecular diamagnetism. Spin paramagnetism is separated in the metallic and semiconducting phase and compared with magnetic resonance results and predictions of available models. 相似文献
9.
The magnetoresistance in spin-ordered state of quasi-one-dimensional (TMTSF)2PF6 has been studied. Both the frequency and anisotropy of the magnetoresistance oscillations are found to be independent of
temperature; this proves the temperature independence of the geometry of two-dimensional closed contours at the Fermi level.
At the same time, the oscillation amplitude decreases with the temperature, indicating the depopulation of the closed contours
in the T = 0 limit. An explanation for the above seemingly controversial results has been proposed.
The text was submitted by the authors in English. 相似文献
10.
Experiments performed on (TMTSF)2PF6 in the spin density wave (SDW) state in the presence of joint ac and dc excitations do not show evidence for coupling between dc and ac response. Irradiation by microwaves does not lead to strong dc nonlinearity, and attempts to resurrect the ESR signal by applied dc currents were also unsuccessful. While the strongly frequency dependent response is indicative of collective effects, the response of the SDW ground state is fundamentally different from that of a charge density wave condensate. 相似文献
11.
S. Cox R.M. Boysel D. Moses F. Wudl J. Chen S. Ochsenbein A.J. Heeger W.M. Walsh L.W. Rupp 《Solid State Communications》1984,49(3):259-263
Resistivity measurements were carried out as a function of temperature and pressure in (TMTSF) 2F2PO2. A strong metal-insulator transition is observed at ~137K which is only incompletely suppressed by high pressures. The nature of the resistivity curves obtained at high pressure suggest the onset of a Fermi surface instability; however, the metallic-like transport at lower temperatures suggests that the energy gap covers only part of the Fermi surface. The surprising increase in ? (T) at temperatures below 20K (under pressure) may result from disorder induced localization arising from the strong electronic scattering from the randomly oriented dipole moments. 相似文献
12.
Kell. Mortensen 《Solid State Communications》1982,44(5):643-647
The thermopower of (TMTSF)2PF6 has been measured along the a-axis as well as along the b-axis. Marked anisotropy is seen in the whole temperature region studied. Close to 100 K, an anomaly is attributed to cross over from dominating one-dimensionality to dominating two-dimensionality. Precursor effects seen in Sa near Tc are attributed to SDW fluctuations. Well below Tc, both thermopower components exhibit typical semiconducting properties. 相似文献
13.
The infrared principal axes of superconducting β-(BEDT-TTF)2I3 are found to be directed along the chain axis and perpendicular to the axis in the a-b plane. At low temperatures well-defined plasma edges appear in both directions. Adopting a simplified 2-D orthorhombic band structure model, effective transfer integrals are found to be . A cross-over from semiconductor-like optical properties at 300 K to metallic-like optical properties at 40 K is observed in both directions. This is the first such observation in any organic conductor. 相似文献
14.
15.
The polarized reflectance spectrum of β-(BEDT-TTF)2PF6 was measured over the spectral range from 720 cm?1 to 25, 000 cm?1 at 293 K (semiconductive phase) and at 318 K (metallic phase). The infrared band found in the conductivity spectrum, which was obtained by the Kramers-Kronig transformation of the reflectance data, is interpreted as the one associated with inter-band transition. 相似文献
16.
The transverse magnetoresistance of (TMTSF)2 ClO4 has been investigated in magnetic fields up to 32 T at several temperatures down to 4.2 K and different angles between B and the crystalline axis. Shubnikov-de-Haas oscillations are observed directly on the magnetoresistance at fields higher than 10 T giving a fundamental field of 259± 10 T in a direction close to c1 axis. 相似文献
17.
T. Vuletić P. Auban-Senzier C. Pasquier S. Tomić D. Jérome M. Héritier K. Bechgaard 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):319-331
The phase diagram of the organic superconductor (TMTSF)2PF6has been revisited using transport measurements with an improved control of the applied pressure. We have found a 0.8 kbar
wide pressure domain below the critical point (9.43 kbar, 1.2 K) for the stabilisation of the superconducting ground state
featuring a coexistence regime between spin density wave (SDW) and superconductivity (SC). The inhomogeneous character of
the said pressure domain is supported by the analysis of the resistivity between T
SDW
and T
SC
and the superconducting critical current. The onset temperature T
SC
is practically constant ( 1.20±0.01 K) in this region where only the SC/SDW domain proportion below T
SC
is increasing under pressure. An homogeneous superconducting state is recovered above the critical pressure with T
SC
falling at increasing pressure. We propose a model comparing the free energy of a phase exhibiting a segregation between
SDW and SC domains and the free energy of homogeneous phases which explains fairly well our experimental findings.
Received 3 September 2001 and Received in final form 9 November 2001 相似文献
18.
Polarized far infrared reflectance measurements from 20 to 330 cm?1 have been made on the organic superconductor (TMTSF)2ClO4. The feature in the reflectance at 28 cm?1 has been studied as a function of temperature and applied magnetic field. Our results suggest that this feature is associated with a coupled electron-phonon mode rather than a pseudogap due to fluctuational superconductivity as has been suggested by others. In addition, a Kramers-Kronig analysis of the reflectance indicates that there is a concentration of oscillator strength above 100–150 cm?1. 相似文献
19.
J.-C. Lasjaunias K. Biljaković D. Starešinić P. Monceau S. Takasaki J. Yamada S.-I. Nakatsuji H. Anzai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):541-550
We report on specific heat measurements of the quasi-one-dimensional organic salt (TMTSF)2AsF6 in its spin density wave state between 75 mK and 7 K. Similarly to (TMTSF)2PF6, we find discontinuities in the lattice contribution at 1.9 K an d 3.5 K ascribed to sub-spin density wave phases. Time-dependent
effects due to dynamics of low-energy excitations in metastable states occur only below 0.2 K which yields an activation energy
for the equilibrium energy relaxation process of 0.34 K, 4-5 times smaller than found for (TMTSF)2PF6. Finally the reduction of the low-energy excitations contribution to the specific heat in comparison to PF6 reveals an intermediate cubic-like regime between 0.25 and 0.5 K that we tentatively describe as the phason contribution
of the incommensurate spin density wave modulation.
Received: 17 March 1998 / Revised: 27 July 1998 / Accepted: 22 September 1998 相似文献
20.
A. Maaroufi C. Coulon S. Flandrois P. Delhaes K. Mortensen K. Bechgaard 《Solid State Communications》1983,48(6):555-559
The physical properties of (TMTSF)2TaF6 are discussed through transport and magnetic measurements. A crossover between two different regimes is observed around 100K and a spin density wave ground state appears below 11 K. The phase diagram under magnetic field is determined. Finally, the properties of this compound are compared with that of the other members of the TMTSF series and the influence of the anion size is discussed. 相似文献